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#Read in the oil spill layer:
ca_oilspill <- read_sf(here("data", "ds394"), layer = "ds394") %>%
clean_names() %>%
rename(name = localecoun)
#Check the projection:
#st_crs(ca_oilspill) #NAD 83 / California Albers, EPSG 3310
#Read in the CA county data shapefile
ca_counties <- read_sf(here("data", "ca_counties"), layer = "CA_Counties_TIGER2016") %>%
clean_names() %>%
select(name)
#Check projection
#st_crs(ca_counties) #WGS 84 / Pseudo-Mercator
#Reset projection
ca_counties <- st_transform(ca_counties, st_crs(ca_oilspill))
#st_crs(ca_counties)
1. Exploratory oil spill location visualization using tmap
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tmap_mode("view")
tm_shape(ca_oilspill) + #Make a tmap map of oilspill locations
tm_dots() + #Where dots represent oil spill events
tm_basemap("Esri.WorldTopoMap") #And the base map is ESRI's topomap
Figure 1. Exploratory interactive map of all (inland and marine) oil spill locations in California in 2008.
2. Chloropleth of inland oil spill events in 2008
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#Wrangling: Want counts of inland oil spill events by county in 2008
modoc <- ca_counties %>%
filter(name == "Modoc") #Make a df with just modoc county for use later
ca_county_oilspill <- ca_counties %>% #Join the two dataframes together
st_join(ca_oilspill)
ca_oilspill_counts <- ca_county_oilspill %>% #Filter for only inland oil spills
filter(inlandmari == "Inland") %>%
group_by(name.y) %>% #Group by county name
summarize(spill_count = n()) #Count oil spill events by county
ggplot(data = ca_oilspill_counts) + #Graph from this count data
geom_sf(aes(fill = spill_count), color = "white", size = 0.1) + #With fill depending on count
scale_fill_viridis() + #Setting the color gradient from viridis package
theme_void() + #With a void theme
labs(fill = "Number of oil spills", #Label for the key
title = "California inland oil spill by county, 2008") + #Label for the map
geom_sf(data = modoc, fill = "lightgray", color = "white", size = 0.1) #Add Modoc county (no spills)
Figure 2. Chloropleth of inland oil spill events in 2008 by California county. Modoc county (gray) had no inland oil spill events in 2008. Los Angeles (yellow) and San Mateo (teal) counties had the two highest counts of inland oil spills (340 and 173, respectively).
Data cited:
California county shapefile data:
“TIGER/Line Shapefiles.” U.S. Census Bureau. Sourced through California Open Data Portal, https://data.ca.gov/dataset/ca-geographic-boundaries
California oil spill data:
“Oill Spill Incident Trackin [ds394]”. California Department of Fish and Game, Office of Spill Prevention and Response. 2008. https://map.dfg.ca.gov/metadata/ds0394.html